Just to add to Richard's pictures of truck springs,
here's a 70 ton National C-1 from p.981 of the 1953 CBC --
o o o
or 2 x 3 x 2 as I would write it. They are turned
45 degrees however, so from the front you see 1
prominent spring, 2 just set back, and all the
others are invisible.
The Barber trucks shown on p.972 have 3 x 3 (S-2A)
3 x 3 (S-2) and 1 x 2 x 2 x 1 (S-1-L) -- in other
words all have 6 springs, and all are 50 ton trucks.
If you're not sure of the capacity of a truck, just
look at the journal dimensions. A 5 1/2 x 10 journal
is 50 tons. A 6 x 11 journal is for 70 tons. This is
the most reliable way to tell a truck's capacity.